Mobile offshore base concepts. Concrete hull and steel topsides

Abstract This paper describes two different types of concepts for a mobile offshore base (MOB). The concepts are hybrids with high strength light weight aggregate concrete (LWC60) in the hull and steel in the topside deck. One concept is a semi submersible type consisting of four identical modules. The MOB is basically 1525 m (5000 ft.) long. The second concept is a single structural unit consisting of a central concrete core 890 m long with a steel cantilever 317 m long at each end. The total length of the unit is 1525 m. Results from detailed code check of fatigue life for the concrete hull is included. It is concluded that fatigue is a “non-issue” for the concrete hull with a design life of 100 years. Possible construction methods and schedules are also presented.